U.S. patent number 7,467,787 [Application Number 10/838,740] was granted by the patent office on 2008-12-23 for compression spring rod.
This patent grant is currently assigned to Barnes Group Inc.. Invention is credited to Jack W. Adoline, Thomas J. Fischer.
United States Patent |
7,467,787 |
Adoline , et al. |
December 23, 2008 |
Compression spring rod
Abstract
A compression spring rod for relatively displacing elements
attached to end mounts of the rod assembly comprises a housing
having a rod member moveable between extended and retracted
positions relative thereto, and a first compression spring in the
housing surrounded by a second compression spring for biasing the
rod member to one of an extended or retracted position relative to
the housing. The two springs are oppositely wound, of different
length, of different outside diameter, and of different wire
diameter whereby, from a compressed condition, the spring rod
exerts an expansion force which increases at a linear rate. Two
sets of the springs can be arranged for biasing the rod member to a
central position relative to the housing.
Inventors: |
Adoline; Jack W. (Toledo,
OH), Fischer; Thomas J. (Whitehouse, OH) |
Assignee: |
Barnes Group Inc. (Bristol,
CT)
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Family
ID: |
27609349 |
Appl.
No.: |
10/838,740 |
Filed: |
May 4, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040207137 A1 |
Oct 21, 2004 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10056941 |
Jan 28, 2002 |
6773002 |
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Current U.S.
Class: |
267/291; 267/290;
267/168 |
Current CPC
Class: |
F16F
3/04 (20130101) |
Current International
Class: |
F16F
1/12 (20060101) |
Field of
Search: |
;267/168,286,289-291,124,129X ;188/312X,322.11,322.16 |
References Cited
[Referenced By]
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3939 118 |
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3939118 |
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195 04 961 |
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Aug 1996 |
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200 00 940 |
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May 2000 |
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200 00940 |
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May 2000 |
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2 772 855 |
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Jun 1999 |
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FR |
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2772855 |
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Jun 1999 |
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FR |
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875291 |
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Aug 1961 |
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GB |
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2036247 |
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Jun 1980 |
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GB |
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57-57934 |
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Apr 1982 |
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JP |
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57057934 |
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Apr 1982 |
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JP |
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11-210312 |
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Aug 1999 |
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JP |
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11210312 |
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Aug 1999 |
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JP |
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Primary Examiner: Schwartz; Christopher P
Attorney, Agent or Firm: Fay Sharpe LLP Turung; Brian E.
Parent Case Text
This patent application is a continuation of U.S. application Ser.
No. 10/056,941 filed Jan. 28, 2002 now U.S. Pat. No. 6,773,002.
Claims
The invention claimed is:
1. A compression spring rod comprising a housing, a rod member, a
guide member, a first bushing, and first and second compression
springs; said housing having an axis, axially opposite first and
second ends, an opening in said first end, and first and second
chambers; said rod member positioned substantially coaxial with
said housing axis and having an inner end in said housing and an
outer end extending axially through said opening in said first end
and outwardly of said first end of said housing, said outer end of
said rod member including a mounting element; said guide member
secured to a portion of said rod member located in said housing,
said guide member at least partially separating said first and
second chambers in said housing; said first bushing positioned at
least closely adjacent to said first end of said housing, said
first bushing including a central region opening designed to at
least partially support said rod member during axial reciprocation
in said housing between fully retracted and fully extended
positions; said first and second compression springs each
positioned in said second chamber of said housing and extending
between said guide member and said second end of said housing, said
first and second compression springs substantially coaxial with
said housing axis, at least one of said first and second
compression springs causing said rod member to move to a
substantially fully extended position when no force along said
housing axis is applied to said outer end of said rod member, at
least one of said first and second compression springs in a
partially compressed state when said rod member is in said fully
extended position, said first spring having a different free length
from said second spring, said first and second compression springs
producing a generally linear spring force as said rod member over a
majority of a distance said rod member moves when moving from a
substantially fully extended position to a substantially fully
retracted position.
2. The compression spring rod as defined in claim 1, wherein said
free length of said first compression spring is greater than said
free length of said second compression spring.
3. The compression spring rod as defined in claim 2, wherein said
first and second compression springs are positioned in said second
chamber such that said first compression spring has a direction of
winding that is different from a direction of winding of said
second compression spring.
4. The compression spring rod as defined in claim 3, including a
guide rod that is secure to said guide member and extends from said
guide member toward said second end of said housing, said guide rod
positioned substantially coaxial to said housing axis, said guide
rod has a shape and a length to enable at least a portion of said
first and second compression spring to surround at least a portion
of said guide rod as said rod member reciprocates between said
fully retracted and said fully extended positions.
5. The compression spring rod as defined in claim 4, including a
tail bushing at least partially positioned in said second end of
said housing, said tail bushing has an inner end and an outer end,
said inner end located in said housing, said inner end has a face
and a neck portion extending outwardly from said face, said neck
portion has a shape and a length to enable at least a portion of
said first and second compression spring to surround at least a
portion of said neck portion as said rod member reciprocates
between said fully retracted and said fully extended positions.
6. The compression spring rod as defined in claim 2, wherein said
first compression spring has an outside diameter that is less than
an outside diameter of said second compression spring, said first
compression spring has a wire diameter that is less than a wire
diameter of said second compression spring, said first compression
spring has a spring rate that is less than a spring rate of said
second compression spring.
7. The compression spring rod as defined in claim 6, including a
guide rod that is secure to said guide member and extends from said
guide member toward said second end of said housing, said guide rod
positioned substantially coaxial to said housing axis, said guide
rod has a shape and a length to enable at least a portion of said
first and second compression spring to surround at least a portion
of said guide rod as said rod member reciprocates between said
fully retracted and said fully extended positions.
8. The compression spring rod as defined in claim 7, including a
mounting element on said outer end of said tail bushing.
9. The compression spring rod as defined in claim 2, including a
guide rod that is secure to said guide member and extends from said
guide member toward said second end of said housing, said guide rod
positioned substantially coaxial to said housing axis, said guide
rod has a shape and a length to enable at least a portion of said
first and second compression spring to surround at least a portion
of said guide rod as said rod member reciprocates between said
fully retracted and said fully extended positions.
10. The compression spring rod as defined in claim 9, including a
tail bushing at least partially positioned in said second end of
said housing, said tail bushing has an inner end and an outer end,
said inner end located in said housing, said inner end has a face
and a neck portion extending outwardly from said face, said neck
portion has a shape and a length to enable at least a portion of
said first and second compression spring to surround at least a
portion of said neck portion as said rod member reciprocates
between said fully retracted and said fully extended positions.
11. The compression spring rod as defined in claim 10, wherein said
first and said second compression springs are designed to provide
substantially all the spring force on said guide member as said rod
member reciprocates between said fully retracted and said fully
extended positions.
12. The compression spring rod as defined in claim 2, including a
tail bushing at least partially positioned in said second end of
said housing, said tail bushing has an inner end and an outer end,
said inner end located in said housing, said inner end has a face
and a neck portion extending outwardly from said face, said neck
portion has a shape and a length to enable at least a portion of
said first and second compression spring to surround at least a
portion of said neck portion as said rod member reciprocates
between said fully retracted and said fully extended positions.
13. The compression spring rod as defined in claim 1, including a
guide rod that is secure to said guide member and extends from said
guide member toward said second end of said housing, said guide rod
positioned substantially coaxial to said housing axis, said guide
rod has a shape and a length to enable at least a portion of said
first and second compression spring to surround at least a portion
of said guide rod as said rod member reciprocates between said
fully retracted and said fully extended positions.
14. The compression spring rod as defined in claim 13, including a
tail bushing at least partially positioned in said second end of
said housing, said tail bushing has an inner end and an outer end,
said inner end located in said housing, said inner end has a face
and a neck portion extending outwardly from said face, said neck
portion has a shape and a length to enable at least a portion of
said first and second compression spring to surround at least a
portion of said neck portion as said rod member reciprocates
between said fully retracted and said fully extended positions.
15. The compression spring rod as defined in claim 14, wherein said
first and said second compression springs designed to provide
substantially all the spring force on said guide member as said rod
member reciprocates between said fully retracted and said fully
extended positions.
16. The compression spring rod as defined in claim 15, including a
guide ring positioned at least partially about said guide member,
said guide ring designed to facilitate a sliding movement of said
guide member within said housing as said rod member reciprocates
between said fully retracted and said fully extended positions.
17. The compression spring rod as defined in claim 15, including a
mounting element on said outer end of said tail bushing.
18. The compression spring rod as defined in claim 1, wherein said
first and second compression springs are positioned in said second
chamber such that said first compression spring has a direction of
winding that is different from a direction of winding of said
second compression spring.
19. The compression spring rod as defined in claim 18, wherein said
first compression spring has an outside diameter that is less than
an outside diameter of said second compression spring, said first
compression spring has a wire diameter that is less than a wire
diameter of said second compression spring.
20. The compression spring rod as defined in claim 19, including a
tail bushing at least partially positioned in said second end of
said housing, said tail bushing has an inner end and an outer end,
said inner end located in said housing, said inner end has a face
and a neck portion extending outwardly from said face, said neck
portion has a shape and a length to enable at least a portion of
said first and second compression spring to surround at least a
portion of said neck portion as said rod member reciprocates
between said fully retracted and said fully extended positions.
21. The compression spring rod as defined in claim 1, wherein said
first and said second compression springs designed to provide
substantially all the spring force on said guide member as said rod
member reciprocates between said fully retracted and said fully
extended positions.
22. The compression spring rod as defined in claim 21, including a
guide ring positioned at least partially about said guide member,
said guide ring designed to facilitate a sliding movement of said
guide member within said housing as said rod member reciprocates
between said fully retracted and said fully extended positions.
23. The compression spring rod as defined in claim 21, including a
mounting element on said outer end of said tail bushing.
24. The compression spring rod as defined in claim 1, wherein said
first compression spring has an outside diameter that is less than
an outside diameter of said second compression spring, said first
compression spring has a wire diameter that is less than a wire
diameter of said second compression spring, said first compression
spring has a spring rate that is less than a spring rate of said
second compression spring.
25. The compression spring rod as defined in claim 1, including a
tail bushing at least partially positioned in said second end of
said housing, said tail bushing has an inner end and an outer end,
said inner end located in said housing, said inner end has a face
and a neck portion extending outwardly from said face, said neck
portion has a shape and a length to enable at least a portion of
said first and second compression spring to surround at least a
portion of said neck portion as said rod member reciprocates
between said fully retracted and said fully extended positions.
26. The compression spring rod as defined in claim 1, including a
guide ring positioned at least partially about said guide member,
said guide ring designed to facilitate a sliding movement of said
guide member within said housing as said rod member reciprocates
between said fully retracted and said fully extended positions.
27. A compression spring rod comprising a housing, a rod member, a
guide member, first and second bushings, and first and second
compression springs; said housing has an axis, axially opposite
first and second ends, an opening in said first end, and first and
second chambers; said rod member positioned substantially coaxial
with said housing axis and has an inner end in said housing and an
outer end extending axially through said opening in said first end
and outwardly of said first end of said housing, said outer end of
said rod member including a mounting element; said guide member
secured to a portion of said rod member located in said housing,
said guide member at least partially separating said first and
second chambers in said housing; said first bushing positioned at
least closely adjacent to said first end of said housing, said
first bushing including a central region designed to at least
partially support said rod member during axial reciprocation in
said housing between fully retracted and fully extended positions;
said second bushing positioned at least closely adjacent to said
second end of said housing; said first and second compression
springs each positioned in said second chamber of said housing and
extending between said guide member and said second bushing, said
first and second compression springs substantially coaxial with
said housing axis, at least one of said first and second
compression springs in a partially compressed state when said rod
member is in said fully extended position, said first spring has a
free length that is greater than a free length of said second
spring, said first and second compression springs producing a
generally linear spring force as said rod member over a majority of
a distance said rod member moves when moving from a substantially
fully extended position to a substantially fully retracted
position, said first and second compression springs positioned in
said second chamber such that said first compression spring has a
direction of winding that is different from a direction of winding
of said second compression spring, said first compression spring
has an outside diameter that is less than an outside diameter of
said second compression spring, said first compression spring has a
wire diameter that is less than a wire diameter of said second
compression spring, said first compression spring has a spring rate
that is less than a spring rate of said second compression
spring.
28. The compression spring rod as defined in claim 27, including a
guide rod that is secure to said guide member and extends from said
guide member toward said second bushing, said guide rod positioned
substantially coaxial to said housing axis, said guide rod has a
shape and a length to enable at least a portion of said first and
second compression spring to surround at least a portion of said
neck portion as said rod member reciprocates between said fully
retracted and said fully extended positions.
29. The compression spring rod as defined in claim 28, wherein said
second bushing has an inner end and an outer end, said inner end
located in said housing, said inner end has a face and a neck
portion extending outwardly from said face, said neck portion has a
shape and a length to enable at least a portion of said first and
second compression spring to surround at least a portion of said
neck portion as said rod member reciprocates between said fully
retracted and said fully extended positions.
30. The compression spring rod as defined in claim 29, wherein said
first bushing includes a cavity designed to telescopically receive
at least a portion of an impact-absorbing spring ring as said guide
rod is moved to said fully extended position, said impact-absorbing
spring ring is positioned between said guide member and said first
bushing.
31. The compression spring rod as defined in claim 30, wherein said
first and said second compression springs are designed to provide
substantially all the spring force on said guide member when said
rod member is in said fully retracted position.
32. The compression spring rod as defined in claim 31, including a
guide ring positioned at least partially about said guide member,
said guide ring designed to facilitate a sliding movement of said
guide member within said housing as said rod member reciprocates
between said fully retracted and said fully extended positions.
33. The compression spring rod as defined in claim 32, including a
mounting element on said outer end of said second bushing.
34. The compression spring rod as defined in claim 33, wherein said
first bushing includes an impact-absorbing cavity, said
impact-absorbing cavity designed to telescopically receive at least
a portion of said guide member when said rod member is in said
fully extended position.
35. The compression spring rod as defined in claim 34, wherein said
first and second compression springs producing a generally linear
spring force as said rod member over substantially the total
distance said rod member moves when moving from a substantially
fully extended position to a substantially fully retracted
position.
36. The compression spring rod as defined in claim 28, wherein said
first bushing includes a cavity designed to telescopically receive
at least a portion of an impact-absorbing spring ring as said guide
rod is moved to said fully extended position, said impact-absorbing
spring ring is positioned between said guide member and said first
bushing.
37. The compression spring rod as defined in claim 28, wherein said
first and said second compression springs designed to provide
substantially all the spring force on said guide member when said
rod member is in said fully retracted position.
38. The compression spring rod as defined in claim 28, including a
guide ring positioned at least partially about said guide member,
said guide ring designed to facilitate a sliding movement of said
guide member within said housing as said rod member reciprocates
between said fully retracted and said fully extended positions.
39. The compression spring rod as defined in claim 28, including a
mounting element on said outer end of said second bushing.
40. The compression spring rod as defined in claim 27, wherein said
second bushing has an inner end and an outer end, said inner end
located in said housing, said inner end has a face and a neck
portion extending outwardly from said face, said neck portion has a
shape and a length to enable at least a portion of said first and
second compression spring to surround at least a portion of said
neck portion as said rod member reciprocates between said fully
retracted and said fully extended positions.
41. The compression spring rod as defined in claim 40, wherein said
first bushing includes a cavity designed to telescopically receive
at least a portion of an impact-absorbing spring ring as said guide
rod is moved to said fully extended position, said impact-absorbing
spring ting is positioned between said guide member and said first
bushing.
42. The compression spring rod as defined in claim 41, wherein said
first and said second compression springs are designed to provide
substantially all the spring force on said guide member when said
rod member is in said fully retracted position.
43. The compression spring rod as defined in claim 42, including a
guide ring positioned at least partially about said guide member,
said guide ring designed to facilitate a sliding movement of said
guide member within said housing as said rod member reciprocates
between said fully retracted and said fully extended positions.
44. The compression spring rod as defined in claim 43, including a
mounting element on said outer end of said second bushing.
45. The compression spring rod as defined in claim 44, wherein said
first bushing includes an impact-absorbing cavity, said
impact-absorbing cavity designed to telescopically receive at least
a portion of said guide member when said rod member is in said
fully extended position.
46. The compression spring rod as defined in claim 45, wherein said
first and second compression springs produce a generally linear
spring force as said rod member over substantially the total
distance said rod member moves when moving from a substantially
fully extended position to a substantially fully retracted
position.
47. The compression spring rod as defined in claim 27, wherein said
first bushing includes a cavity designed to telescopically receive
at least a portion of an impact-absorbing spring ring as said guide
rod is moved to said fully extended position, said impact-absorbing
spring ring is positioned between said guide member and said first
bushing.
48. The compression spring rod as defined in claim 27, wherein said
first and said second compression springs designed to provide
substantially all the spring force on said guide member when said
rod member is in said fully retracted position.
49. The compression spring rod as defined in claim 27, including a
guide ring positioned at least partially about said guide member,
said guide ring designed to facilitate a sliding movement of said
guide member within said housing as said rod member reciprocates
between said fully retracted and said fully extended positions.
50. The compression spring rod as defined in claim 27, including a
mounting element on said outer end of said second bushing.
51. The compression spring rod as defined in claim 27, wherein said
first bushing includes an impact-absorbing cavity, said
impact-absorbing cavity designed to telescopically receive at least
a portion of said guide member when said rod member is in said
fully extended position.
52. The compression spring rod as defined in claim 27, wherein said
first and second compression springs produce a generally linear
spring force as said rod member over substantially the total
distance said rod member moves when moving from a substantially
fully extended position to a substantially fully retracted
position.
Description
BACKGROUND OF THE INVENTION
The present invention relates to compression spring rods, and more
particularly, to a spring and rod assembly that exerts an
expansional force which increases at a linear rate.
The invention relates to a mechanism for biasing hoods, tops,
doors, hinged covers, and other elements from a closed to an open
position. The invention involves the use of springs in conjunction
with a rod member to exert the driving force on the elements to be
displaced. The following patents are incorporated herein by
reference as background information with regard to spring
mechanisms: U.S. Pat. No. 6,199,843 to DeGrace; U.S. Pat. No.
5,810,339 to Kuspert, et al.; and U.S. Pat. No. 4,962,916 to
Palinkas.
Compression spring rods are used in various applications, for
example, to assist in lifting, opening, and damping. Typical
applications include lifting a lid hinged to a stationary base.
Other applications include lifting and/or balancing elements for
the trunk or hatchback of an automobile. Still another application
includes a damping spring for closing a door hinged to a stationary
frame. Most applications involve the use of a pneumatic or gas
spring to assist the opening motion. Many of these types of
compression spring assemblies contain either gas or hydraulic fluid
to control forces and piston speeds. Consequently, because these
products contain a gas and/or fluid, they are subject to premature
failure, due to the leakage of the gas or fluid over time. The
leakage results in a loss of control forces and a subsequent loss
of spring life.
SUMMARY OF THE INVENTION
The present invention provides an improved compression spring rod
which overcomes the above referred-to difficulties and others with
regard to such rods heretofore available. More particularly in this
respect, a compression spring rod in accordance with the invention
is particularly adapted for lifting or pivoting one component
relative to another component at a controlled rate. In accordance
with one aspect, the invention provides a lift mechanism for hinged
covers and the like that operates automatically upon release of the
cover, or a lift mechanism for a loaded platform wherein the
platform is elevated, progressively, as the load thereon is
reduced. Advantageously, the compression spring assembly applies a
constant and controlled force to open the cover or lift the
platform. The mechanism is able to support significant loads while
maintaining strength over a greater number of operating cycles than
existing pneumatic or gas spring designs. Further, the invention
provides a purely mechanical compression rod assembly that can
yield controllable forces over a long period of use and control the
spring forces during both extension and compression.
A compression spring rod according to the invention is comprised of
multiple compression springs. The compression spring rod assembly
includes a rod which is adapted to extend and retract relative to a
housing. In one application, for example, the compression springs
will build potential force as the springs are compressed, and
release that force once the springs are allowed to expand. This
extension of the springs imparts a force to the parts connected to
the ends of the rod and housing and, advantageously, multiple end
configurations can be used to adapt the spring rod to a variety of
mounting applications. The compression springs of a spring rod
according to the invention are interrelated to produce a linear
load versus deflection curve. The encased springs minimize load
losses over time, and the mechanism does not contain any fluid or
gases within the lift body. This advantageously eliminates the
inevitable problem of leakage and subsequent loss of utility.
It is accordingly an outstanding object of the present invention to
provide an improved compression spring rod for exerting an
operating force on a displaceable member at a controlled rate.
Another object of the invention is the provision of a compression
spring rod that supplies a consistent force over an extended period
of time and maintains strength over a greater number of cycles
compared to compression spring rods heretofore available.
Yet another object of the invention is the provision of a
compression spring rod having at least two compression springs
interrelated to produce a linear load versus deflection curve.
Yet another object of the invention is the provision of a
compression spring rod having at least two compression springs
interrelated to minimize load losses over time.
A further object of the invention is the provision of a mechanical
compression spring rod assembly that provides an operating force
that increases at a linear rate.
Yet a further object of the invention is to provide a mechanical
compression spring assembly that can accommodate, selectively,
multiple end configurations, thus adapting the assembly for
mounting in a wide variety of use applications.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects and advantages will in part be
obvious and in part pointed out in the following description taken
together with the accompanying drawings in which:
FIG. 1 is a side elevation view, partially in section, of a
compression spring rod according to the invention in the extended
position;
FIG. 2 is a longitudinal cross section view of the compression
spring rod in the compressed position;
FIG. 3 is a cross sectional view taken along line 3-3 of FIG.
2;
FIG. 4 is an exploded perspective view of the component parts of
the compression spring rod shown in FIGS. 1-3;
FIG. 5 is a side elevation view of the compression springs of the
compression spring rod;
FIG. 6 is a graph illustrating the relationship between spring
force and compression of the compression spring rod assembly;
FIG. 7 is a perspective view of a box with a lid pivotable about a
horizontal axis and compression spring rod elements shown in FIGS.
1-3 between the box and lid;
FIG. 8 is a side elevation view, in section, of a spring rod in
accordance with a second embodiment of the invention;
FIG. 9 is an exploded perspective view of the component parts of
the compression spring rod shown in FIG. 8;
FIG. 10 is a perspective view illustrating a use of the compression
spring rod of FIGS. 8 and 9;
FIG. 11 is a side elevation view, in section, of a spring rod in
accordance with another embodiment of the invention;
FIG. 12 is an exploded perspective view of the component parts of
the compression spring rod shown in FIG. 11; and,
FIG. 13 is an illustration of an application of the compression
spring rod of FIGS. 11 and 12.
DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
Referring now in greater detail to the drawings, wherein the
showings are for the purpose of illustrating preferred embodiments
of the invention only, and not for the purpose of limiting the
invention, a compression spring rod 10, in accordance with the
invention, as shown in FIGS. 1-6, has an axis 11 and includes a rod
member 22 which is axially extendable and retractable relative to a
one-piece tubular housing 24. Rod 22 has an outer end 22a and an
inner end 22b connected to a guide rod 26 as set forth more fully
hereinafter. Guide rod 26 extends axially inwardly of inner end 22b
of rod 22 and is surrounded by a first compression spring 28 which
is supported by the exterior surface 46 of guide rod 26 against
buckling. First compression spring 28 is surrounded by a second
compression spring 30 which is supported against buckling by the
interior surface 48 of housing 24. Alignment of compression springs
28 and 30 relative to one another and axis 11 is maintained by the
exterior surface 46 of guide rod 26 in conjunction with the
interior surface 48 of housing 24. Housing 24 has a mounting end 23
and an outer or opposite end 25, and compression springs 28 and 30
are axially captured between a tail bushing 38 at mounting end 23
and a guide member 34 mounted between guide rod 26 and the inner
end 22b of rod 22 as set forth hereinafter. Tail bushing 38 is
supported in housing 24 by bending the endmost portion of the
housing radially inwardly to define a retaining flange 39.
Compression spring rod 10 involves the use of a one-piece housing
24 which facilitates smooth movement of lift rod 22 and compression
springs 28 and 30 during operation of the spring rod. As shown in
the exploded view of FIG. 4, tail bushing 38 includes a neck
portion 42 having a diameter sized to be received in the interior
of compression spring 28. Tail bushing 38 also has a threaded stud
44 distal to the neck portion 42 which is received in a threaded
recess 17 in a mounting element 18. Guide rod 26 includes a
threaded stud 52 at the outer end thereof which passes through an
opening 58 in guide member 34 and into a threaded bore 54 provided
therefor in rod 22. Lift rod 22 passes through an opening 72
through a rod bushing 32 at outer end 25 of housing 24, and has a
threaded stud 70 on outer end 22a thereof which is received in a
threaded recess 27 provided therefor in a mounting element 20.
Mounting elements 18 and 20 have openings 19 and 21 therethrough,
respectively, for receiving a variety of different mounting
components common in the industry including, for example, pins,
bolts, swivels, and the like. Advantageously, the threaded studs 44
and 70 at opposite ends of the spring rod assembly provide for
accommodating the use of different mounting elements than those
shown so as to modify the assembly for use in a variety of
structural environments.
Guide member 34 is slidable in housing 24 and includes a guide ring
35 of suitable material to facilitate such sliding movement. Rod 22
is slidably supported at end 25 of housing 24 by rod bushing 32
which is secured to the housing by a pair of set screws 40 having
inner ends received in an annular recess 41 in the rod bushing. Rod
bushing 32 is further axially retained in housing 24 by bending the
outermost part of end 25 radially inwardly to provide a retaining
flange 33. At full extension, rod 22 is cushioned by rod bushing 32
and an impact absorbing metal spring ring 36 received in a recess
55 at inner end 22b of rod 22 adjacent the axially outer face of
guide member 34. When rod 22 is fully extended, spring ring 36
engages in a recess 51 in the axially inner end of rod bushing 32.
Lubrication can be provided in housing 24 to facilitate the sliding
movement of guide member 34 therein. As will be appreciated from
the foregoing description, guide member 34 and rod bushing 32
support rod 22 for reciprocation in housing 24 such as to maintain
minimal breakaway forces for rod 22. Additionally, guide member 34
and rod bushing 32 keep rod 22 coaxial with axis 11 and decrease
the effect of side loading on the assembly.
Compression spring rod 10, through the multiple spring rate
characteristics of compression springs 28 and 30, serves to provide
smooth extension forces to the movement of lift rod 22 from the
retracted to the extended position thereof relative to housing 24.
Depending upon the application, the appropriate load versus
deflection can be determined and the corresponding physical and
elastic properties of the combination of compression springs 28 and
30 can then be ascertained. The compression springs 28 and 30 can
each be fabricated from spring material, such as music wire, and,
for example, ASTM A228 or 302 stainless steel.
Each compression spring 28 and 30 has a different stress and strain
characteristic. If the spring is considered to be a one-dimensional
object, the only stress will be extensional (or compressional,
which will be the negative of extensional) and the units of stress
will be force per unit of extension. Within a range of compression,
each spring obeys "Hook's Law", which states that for forces in a
defined range, the stretch of a material is proportional to the
applied force: F=-k.DELTA.L The proportionality constant, k, is
known as the spring constant with dimensions of force over length,
and .DELTA.L is the amount of compression. The negative sign
indicates that the force is in the opposite direction of extension:
if the spring is extended, the force tries to restore it to its
original length. Likewise, if the spring is compressed
(.DELTA.L<0), the force attempts to expand the spring, again to
its original length. The spring constant depends on both physical
and elastic properties of the material being stretched. Hook's Law
is fairly intuitive at a basic level, and can be illustrated by
everyday experience in which it is known that a thin wire will
stretch more than a thick wire or rod of the same material when the
same stretching force is applied to both. The formula
U=1/2k(.DELTA.L).sup.2, gives the work of extension (U) or
alternatively, the amount of potential energy stored in the
spring.
As shown in FIGS. 3 and 5, compression spring 28 has a free length
L1 which is greater than the free length L2 of spring 30, and
spring 28 has an outer diameter smaller than that of compression
spring 30. Also, the wire diameter of spring 28 is less than that
of spring 30, and the spring rate of spring 28 is less than that of
spring 30. As an example of one particular application, the
specific physical characteristics of compression spring 28 are:
wire diameter 0.055'', inside diameter 0.5444'', outside diameter
0.6544'', free length 17.2'', and a spring rate of 0.95 lbs./inch;
and the physical characteristics of compression spring 30 are: wire
diameter 0.081'', inside diameter 0.675'', outside diameter
0.837'', free length 13.8'', and a spring rate of 3.37 lbs./inch.
FIG. 6 displays the load versus deflection curve for compression
springs 28 and 30 having the foregoing specifications, and for the
combined springs in the assembly shown in FIGS. 1 and 2. It is to
be noted that springs 28 and 30 are oppositely wound and that this
interrelationship together with the dimensional characteristics of
the springs produces the combined linear load versus deflection
graph depicted in FIG. 6. The different free lengths, as shown in
FIG. 5, of springs 28 and 30 is one component that helps to control
the forces and stabilize the guide member 34 and rod 22 during
initial displacement thereof from the position shown in FIG. 1 to
the position shown in FIG. 2 and during the termination of the
movement from the position shown in FIG. 2 to the position shown in
FIG. 1. In this respect, the longer spring 28 is, in the free state
of the spring 30 shown in FIG. 1, slightly compressed to the length
of the latter spring and, therefore, exerts a stabilizing force on
the components which eliminates any free play during initial and
terminal displacement thereof during use.
FIG. 7 illustrates two compression spring rods 10 according to the
invention connected between a box 12 and a lid 14 therefor. While
not shown in detail, lid 14 is suitably mounted on box 12, such as
by hinges, to be pivotable about an axis A relative thereto. The
mounting elements 18 and 20 of compression spring rods 10 are
suitably secured to box 12 and lid 14, respectively. A latch 15 is
shown on lid 14 for engagement with a keeper 16 on box 12 to
releasably hold the lid closed relative to box 12. Latch 15 may be
of various types common in the industry, and the method for
releasing latch 15 may be by hand, foot, key, remote, etc.
Subsequent to releasing the latch 15, compression spring rods 10
automatically extend from the position shown in FIG. 2 to the
position as shown in FIG. 1, during which the spring rods 10
expand, releasing the stored compressive force in compression
springs 28 and 30 to displace lid 14 from the closed to the open
position thereof.
FIGS. 8 and 9 illustrate another embodiment of a compression spring
assembly according to the invention. In this embodiment,
compression spring rod 100 has an axis 101 and includes a rod 102
which is axially extendable and retractable relative to a one-piece
tubular housing 104. Rod 102 has an outer end 102a and an inner end
102b connected to a guide rod 106 as set forth more fully
hereinafter. Guide rod 106 extends axially inwardly of inner end
102b of rod 102. A first compression spring 108 is supported
against buckling by the exterior surface 103 of rod 102. Spring 108
is surrounded by a second compression spring 110 which is supported
against buckling by the interior surface 105 of housing 104.
Coaxial alignment of compression springs 108 and 110 relative to
one another and axis 101 is maintained by the exterior surface 103
of rod 102 in conjunction with the interior surface 105 of housing
104. When assembled, compression springs 108 and 110 are axially
captured between a rod bushing 112 at end 114 of housing 104 and a
guide member 116 secured to inner end 102b of the rod between the
latter and guide rod 106. Guide rod 106 includes a threaded stud
107 at the outer end thereof which passes through an opening 115 in
guide member 116 and into a threaded bore 137 provided therefor in
rod 102. A tail bushing 120 is supported in end 124 of housing 104
by set screws 122 received in an annular recess 126 in the tail
bushing 120. For the purpose set forth hereinafter, the component
parts of spring rod 100 are cushioned during operation of the
compression spring assembly by a cushioning spring 130 which
surrounds guide rod 106. Spring 130 is axially captured between the
tail bushing 120 at end 124 and the guide member 116. Tail bushing
120 includes a neck portion 123 having a diameter sized to be
received in the interior of cushioning spring 130. Tail bushing 120
also has a threaded stud 125 distal to neck portion 123 which is
received in a threaded recess 127 in a mounting element 132. Guide
member 116 is slidable in housing 104 and includes a guide ring 117
of suitable material to facilitate such sliding movement. Rod 102
is slidably supported at end 114 of housing 104 by rod bushing 112
which is secured to housing 104 by a pair of set screws 122 having
inner ends received in an annular recess 113 in bushing 112. Rod
102 passes through an opening 111 in bushing 112 at outer end 114
of housing 104, and has a threaded stud 139 on outer end 102a
thereof which is received in a threaded recess 140 provided
therefor in a mounting element 134. As will be appreciated from the
foregoing description, guide member 116 and rod bushing 112 support
rod 102 for reciprocation in housing 104 such as to maintain
minimal breakaway forces for rod 102. Mounting elements 132 and 134
have openings 133 and 135 therethrough, respectively, for receiving
a variety of different mounting components common in the industry
including, for example, pins, bolts, swivels, and the like.
Mounting element 132 is fixedly attached to tail bushing 120 for
mounting the compression spring assembly to a work supporting
surface.
FIG. 10 illustrates four compression spring rods 100 each connected
between a corresponding fixed support 142 and a platform or work
supporting table 140. The spring rods 100, as shown in FIG. 10, are
designed to expand in the direction of arrow z in response to a
load applied to platform 140, thus compressing springs 108 and 110.
Compression springs 108 and 110 then expand and retract the spring
rods in the direction of arrow y as the load is progressively
removed from platform 140. Compression springs 108 and 110 have the
same physical characteristics as compression springs 28 and 30
described in the first embodiment. The arrangement of spring rods
100 and platform 140 as shown in FIG. 10 is suitable, for example,
as a progressive load lifter, such as for metal plates. As plates
are progressively stacked on platform 140, the spring rods 100
extend in the direction of arrow z, whereby the compression springs
108 and 110 are progressively compressed. As stated, when the
springs are compressed (.DELTA.L<0) the resultant force attempts
to expand the spring rod to its original length. Thus, as the
plates are progressively removed from the platform, the compression
springs 108 and 110 expand thereby causing the platform 140 to move
in the direction of arrow y. In this manner, the springs provide
controlled forces by which the top plate in the stack on the
platform remains at a given level as the platform moves first in
the z direction and then in the y direction. If the entire load is
suddenly removed from the platform, the spring rods retract rapidly
and cushioning spring 130 cushions the retracting movement to
protect the spring rods against damage. Additionally, it will be
appreciated that this embodiment is particularly well suited as a
counterbalance system, conveyor chain tensioner, door lift assist,
and dampener.
FIGS. 11 and 12 illustrate another embodiment of a compression
spring assembly according to the invention. In this embodiment,
compression spring rod 180 has an axis 181 and includes two rods
182 and 184 which are alternately axially extendable and
retractable together relative to a one-piece tubular housing 186.
Rod 182 has an outer end 182a and an inner end 182b and rod 184 has
an outer end 184a and an inner end 184b connected to inner end 182b
of rod 182 together with a guide member 200 as set forth more fully
hereinafter. Rod 182 extends axially inwardly of end 186a of
housing 186 and is surrounded by a first compression spring 188
which is supported by the exterior surface 183 of rod 182 against
buckling. First compression spring 188 is surrounded by a second
compression spring 190 which is supported against buckling by the
interior surface 187 of housing 186. Rod 184 extends axially
inwardly of opposite end 186b of housing 186 and is surrounded by a
third compression spring 192 which is supported by the exterior
surface 185 of rod 184 against buckling. Third compression spring
192 is surrounded by a fourth compression spring 194 which is
supported against buckling by the interior surface 187 of housing
186. Alignment of compression springs 188, 190, 192, and 194
relative to one another and axis 181 is maintained by the exterior
surfaces 183 and 185 of rods 182 and 184, respectively, in
conjunction with the interior surface 187 of housing 186.
Compression springs 188 and 190 are axially captured between a rod
bushing 196 at end 186a and the guide member 200, and compression
springs 192 and 194 are axially captured between a rod bushing 202
at end 186b of the housing and the guide member. Rod bushing 196 is
supported in housing 186 by set screws 206 at end 186a thereof
which extend into an annular recess 197 in bushing 196. Similarly,
rod bushing 202 is supported in housing 186 by set screws 206 at
end 186b thereof which extend into an annular recess 203 in the
bushing. Axial retention of bushings 196 and 202 is further
enhanced by bending the corresponding end of housing 186 radially
inwardly of the bushings.
The compression spring rod 180 involves the use of a one-piece
housing 186 which facilitates smooth movement of rods 182 and 184
and compression springs 188, 190, 192, and 194 during operation of
the spring rod. As shown in the exploded view of FIG. 12, rod 184
includes threads 230 and 231 at opposite ends of the rod. Threads
230 are received in a threaded recess 232 in a mounting element
220. Threads 231 pass through an opening in spring ring 210, an
opening through guide member 200, and an opening in spring ring 208
and are received in a threaded recess 235 in rod 182. Rod 182
includes threads 234 distal to recess 235, which are received in a
threaded recess 233 in a mounting element 222. As will be
appreciated from the foregoing description, guide member 200 and
rod bushings 196 and 202 support rods 182 and 184, respectively,
for reciprocation in housing 186 such as to maintain minimal
breakaway forces for rods 182 and 184 in use of the spring
assembly.
Spring rod assembly 180 is adapted to apply an extension force,
alternately, in axially opposite directions at a controllable rate.
At full extension from housing 186, rods 182 and 184 are cushioned
by rod bushings 196 and 202, respectively. In addition, impact in
the direction of extension is absorbed by metal spring rings 208
and 210 which are received in recesses 212 and 214, respectively,
at inner end 182b of rod 182 and inner end 184b of rod 184. Spring
rings 208 and 210 are adjacent the axially outer faces of guide
member 200 and respectively bottom on rod bushings 196 and 202, but
separated by their respective compression springs 188 and 192, upon
full extension of the rods in the respective direction of
extension. Lubrication can be provided in housing 186 to facilitate
the sliding movement of guide member 200 therein.
As shown in FIG. 13, spring rod assembly 180 is capable of
self-centering a load which, as illustrated by way of example only,
is in the form of two workpieces 230 and 232 having ends 230a and
232a pivotally attached to a fixed support member 231. Spring rod
180 has the outer ends of rods 182 and 184 thereof respectively
pivotally connected to ends 232b and 230a of the workpieces. Spring
rod 180 is supported centrally between workpieces 230 and 232 by a
bracket 224 rigidly secured to support member 231 by a support arm
225. The springs of each pair of compression springs 188 and 190
and 192 and 194 have the same physical characteristics as
compression springs 28 and 30 described in the first embodiment. In
the arrangement shown in FIG. 13, spring rod 180 is a load
centering assembly. In this respect, it will be appreciated that if
either workpiece 230 or 232 is displaced in the direction of arrow
c, rod 184 extends relative to housing 186 and the springs 192 and
194 are compressed. The resultant force of springs 192 and 194 in
the direction of arrow e attempts to expand the springs to their
original length. It will be appreciated that the opposite is true
when either workpiece is displaced in the direction of arrow d. In
this respect, springs 188 and 190 are compressed and springs 192
and 194 are totally relaxed. The resultant force in the direction
of arrow f attempts to expand springs 188 and 190 to their original
length. During return movement of workpieces 230 and 232 to the
central position thereof, the relaxed pair of springs cushion the
return movement. As with the earlier embodiments, the springs 188
and 190 and 192 and 194 provide controlled forces to self-center
workpieces 230 and 232 when either is deflected from the neutral
position. It will be appreciated that this embodiment is
particularly well suited as a centering device in a steering
mechanism, linkage mechanism, gating mechanism, and dampener.
While considerable emphasis has been placed herein on the
structures and configurations of the preferred embodiments of the
invention, it will be appreciated that other embodiments, as well
as modifications of the embodiments disclosed herein, can be made
without departing from the principles of the invention. In this
respect, it will be appreciated that the spring rod can be used in
applications other than those disclosed herein. Similarly, multiple
combinations of coaxial and surrounding springs (i.e. three, four,
etc.) may be configured to meet the desired load versus deflection
for a particular application. Likewise, it will be appreciated that
a spring rod according to the invention can be secured to
relatively displaceable components in any number of different ways.
These and other modifications of the preferred embodiments, as well
as other embodiments of the invention, will be obvious and
suggested to those skilled in the art from the disclosure herein,
whereby it is to be distinctly understood that the foregoing
descriptive matter is to be interpreted merely as illustrative of
the present invention and not as a limitation thereof.
* * * * *